Abstract Among the variety of tissue-resident NK-like populations recently distinguished from classical recirculating cNK cells, liver innate lymphoid cells type I (ILC1) have been shown to represent a distinct lineage that originates from a novel PLZF-expressing ILC precursor (ILCP) strictly committed to the ILC1, ILC2 and ILC3 lineages. Here, using PLZF-reporter mice and cell transfer assays, we studied the developmental progression of ILC1s and demonstrated substantial overlap with stages previously ascribed to the cNK lineage, including pre-pro-NK, pre-NK precursor (pre-NKP), refined NKP (rNKP) and immature NK (iNK). Although they originated from different precursors, the ILC1 and cNK lineages followed a parallel progression at early stages and diverged later at the iNK stage, with a striking predominance of ILC1s over cNKs early in ontogeny. While a limited set of ILC1 genes were dependent on PLZF for expression, characteristically including Il7r, most of these genes were also differentially expressed between ILC1s and cNKs, indicating that PLZF together with other, yet to be defined, factors contribute to the divergence between these lineages.